Plug type circuit breaker



L. SCHMIDT 2,111,943

PLUG TYPE CIRCUIT BREAKER Filed Dec. 16, 1935 INVENTOR Patented Mar. 22, 1938 UNITED STATES PATENT OFFICE lllllli PLUG TYPE @IRCUIT BREAKER Lambert Schmidt, Leeds, N.. il'. Application December ld, 1935, Serial No.. 54,533

15 Claims.

The present invention relates to electrical circuit breakers of. the plug type. More particularly, the invention relates to plug type circuit breakers wherein the circuit is maintained closed by the positive action of a thermal element which is connected directly in the electrical circuit which is to be controlled by the circuit breaker. Ex'- amples of this type of circuit breaker are found in aplicants Patents Nos. 2,083,508 and 2,083,509,

issued June 8, 1937, and the present invention relates to improvements inthe structure of these circuit breakers by means of which the operation is rendered more effective and the life and dependability of the device greatly increased.

Heretofore wires or plates of zinc have been used as protective devices for ordinary lighting and industrial circuits. inasmuch as such fuses require a substantial current to melt or destroy them they do not function eifectively as protec` tive devices for the ordinary electrical circuits. particularly where such circuits are to be protected against comparatively slight currents. Accordingly, various attempts have been made to utilize circuit breakers as protective. devices for circuits of the above character. Such circuit breakers have been relatively large and cannot be used in the space which has heretofore been provided for the ordinary zinc wire or plate fuses and the relatively large size of such circuit breakers, and the comparatively great expense involved in the manufacture thereof, have prevented the use thereof for protecting the ordinary lighting and industrial circuits.

In accordance with the present invention a circuit breaker has been provided which does not require magnetic devices to control the operation thereof or to extinguish the arc formed when the circuit breaker opens. In addition to providing a new and effective means for releasing the circuit breaker, the construction is of such character as to provide an effective means to prevent arcing and consequent destruction of the breaker contacts. Moreover, the construction is of such size and character as to enable the circuit breaker to be used in the receptacle in which zinc wire or plate fuses have heretofore been used and, as a result of the above construction, the cost of the circuit breaker constructed in accordance with the present invention has been reduced to a minimum which enables the device to be used A at a cost which is comparable, quite favorably,

vwith the cost of zinc Wire fuses.

In this connection, it is an object of the pres- 55 ent invention to reduce the size of the mecha- (Cl. 20G-M6) nism substantially without impairing the operan tion thereof.

A further object of the invention is to provide a plug type circuit breaker having an improved form of free tripping mechanism, by means of which the contacts may be maintained in a dis-u engaged condition as long as an overload exists in the line, regardless of the actuation of the manual breaker closing elements.

A further object of the invention is to provide, 10 in a circuit breaker of the above character, an improved guide and positioning member by means of which the movable breaker contact is effectively guided during motion thereof into a closed position. 15

A further object of the invention is to provide a circuit breaker of the above character wherein the effect of the thermal element may be varied by means of variation of the tension of the spring which normally urges the movable contact into 20 an open position.

Further objects of the invention will be apparent as it is described in greater detail in connection with the accompanying drawing, wherein Figure l is a View in section, taken in a plane 25 passing through the axis of a plug type circuit breaker construction in accordance with the pres= ent invention. The section upon which Figure 1 is taken is illustrated by the line l-l of Figure 2;

Figure 2 is a view in section, taken on the line 2--2 of Figure 1, and looking in the direction of the arrows;

Figure 3 is a view in section taken on the line 3-3 of Figure l, and looking in the direction of 35 the arrows;

Figure Li is a view in section taken on the line ll-l of Figure l, and looking in the direction of the arrows; and

Figure 5 is a view similar to Figure l, showing 40 the breaker contacts in closed position.

With reference to the above drawing, a plug type circuit breaker is shown as being formed with a base portion itl and a cover portion il. The base portion is formed to receive a threaded 45 shell i2 which is adapted tol be threaded into the usual socket and to form one terminal for the electrical circuit within the circuit breaker. A 'button i3 is carried upon the bottom of the base portion lil and serves as the other terminal of the above electrical circuit, being secured to the base portion by means of a stem i4 which entends through the bottom wall and is flanged over to engage a bottom plate l5. The cover l I is formed with a side wal?. it which is received about a flange I'I and may be suitably secured thereto. The central portion of the cover I I is formed with an upwardly extending wall I3 having a iianged over portion I9 to receivea button 23 slidably therein. 'I'he button 20 is formed with an outwardly ilanged portion 2l to engage the flanged over portion I9 and thus limit the outward movement of the button 2lil with respect to the cover II.

Upon the bottom portion III is provided a plate 22 having one or more pigtails 23 which extend downwardly through apertures 24 in the bottom portion I0 and contact electrically with the threaded shell I2. The plate 22 may be formed with a cylindrical guide sleeve 25 within which a hollow tube 25 is slidably mounted. The upper end of the tube 26 is provided with a iianged member 21 which is threadedly secured thereto in order that the axial position of the flanged member 21 may be adjusted with respect to the tube 26. A spring 28 is positioned between the flanged member 21 and the mounting plate 22 and normally urges the tubular member 26 upwardly into the position shown in Figure 1.

A separate spring 29 is provided beneath the button 20 and between the same and the plate 22 in order to urge the button into the position illustrated in Figure 1. In this manner, relative motion between the tube 26 and the button' 23 is provided, while, at the same time, normally biasing the said members 2li and 26 in the open position, as illustrated in Figure l.

Upon the stem I4 is provided a central guide tube 30 which is formed of insulating material and received within the tubular member 26 and is mounted upon the stem with provision for a degree of pivotal motion by means of a screw 3|. By permitting a certain limited amount of motion between the guide tube 30 and the stem I4, the tube 36 aligns itself properly with the hollow tube 26 and ties the elements of thecircuit breaker together in an eifective manner and in such fashion that eilective operation of the device at all times is insured.

Upon the hollow tube 26 is secured a plate 32 which may serve as a stop to limit motion of the tube 26 in the direction in which the tube moves during operation of the breaker contacts. The plate 32 is formed with a reversely and downwardly extending portion 33 which is formed with an aperture 34 through which the tube 26 extends, thus permitting a certain amount of swinging motion of the plate 33 with respect to the tube 26. At the end of the extension 33, a contact 35 is provided, this contact preferably being of a graphite compound in order to provide a high resistance to the flow of an electric current and also to the destructive effect of arcing. Contact 35 is adapted to have sliding engagement with an elongated curved stationary contact member 36 which is mounted upon the base plate I5, electrical connection between contacts 35- and 36 being maintained after the main breaker contacts to be described presently have been broken. A guide rod 31 extends downwardly from the mounting plate 22 and is received within a notched portion 38 at the bend between the plate 32 and its extension 33.

The lower end of the hollow tube 26 is formed with a rounded portion 39 and serves as the movable breaker contact which coacts with a stationary breaker contact 40. .y l

The stationary contact member 40 is mounted upon the base plate I5 by means of a screw 4I and is formed as a bi-metal element having a portion 42 and a reversely extending portion 43. Each of the portions 42 and 43 is formed with a bulge 44, the portion 43 terminating in an outwardly extending or flaring portion 45. The portions 42 and 43 with the bulges 44 therein are thus electrically connected to the bottom plate I5 and button I3 and constitute the stationary breaker contact, the natural resiliency of the portions normally urging the same together in order to tightly embrace the movable contact 33 when' it is moved into the .bulged portions 44 of the stationary contact. In this fashion, when the current flowing' through the circuit breaker does not exceed a predetermined maximum, the frictional gripping and clutching effect of the stationary contact member 40 is sufficient to hold the movable contact 39 and the hollow tube 26 in the closed position against action of the spring 23. When the current flowing through the circuit breaker exceeds a predetermined maximum, the resulting heating of the bi-metal element 4l causes the same to expand and release the contact 39 and hollow tube 26. As the contact is broken between the contact members 39 and 46, the high resistance or shunt contact members 35 and 36 limit the current for a short time in order to prevent arcing between the contact members 39 and 43.

In. order to prevent injury to the device by maintaining the button 2li in adepressed condition during such time as an overload exists on the line. a free tripping device is provided and consists of one or more arms 46 which are secured at 41 to the button 20 and which extend downwardly in alignment with the tubes 26 and 39. Each of the arms 46 is provided with a pressed-out detent 46 which is adapted to engage the upper end of the hollow tube 26 in order that the downward motion of the button 2li may be transmitted to the tube 26. In this fashion, the tube 26 is carried with the button 20 and moved into engagement with the stationary contact 40 to close the circuit. Upon engagement of the movable contact 39 with the contact 40, thedetents 43 are released from the hollow tube 26 to permit the tube 26 to be moved to the open position by the spring 26 when the bi-metal element forming the contact 40 is heated sulciently. Such release is eil'ected by providing a cam surface 43 on each of the arms 46, such cam surface being engaged by the upper end of the tube 39 which is rounded internally as at 50. The rounded portion of the tube 30 thus engages the cam surfaces 49 and, upon continued downward motion of the button 20, causes the arms 46 to be moved inwardly to release the detents 43 thereon from engagement with the upper end of the tube 26. This position is illustrated in Figure 5. In order that the condition of the circuit breaker may be indicated effectively, a plunger 5I may be slidably received in the cover I0. This plunger 5I may be suitably colored and normally urged into a retracted or non-indicating position by means of a spring 52 which engages a ange 53 formed on the plunger. In order that the plunger may be urged upwardly into an indicating position, an arm 54 is provided which may be secured to the plunger 5I and have a downwardly extending portion engaging the plate-32. In this fashion, when the contacts of the circuit breaker are open, the arm 54 moves the plunger 5I into an indicating position to show that the circuit breaker has been operated. Manual release of the closed contacts is etl'ected by means of an arm 55 which is pivoted at 56 upon II and bottom member the plate 22 and which is formed with a head 51 of suitable insulating material at the lower end thereof. This head is received between the adjacent ends of the bi-metai element 40, thus causing swinging motion of the arm 55 toward the hollow vtube 26 to cause the head 51 to spread the members 42 and l43 and release the movable contact. Such swinging motion of the arm 55 is accomplished by means of an angular extension 58, the upper end of this extension being actuated by means of a button 59 which is slidably received within the 'cover Il. Pressure upon the button 59 thus is transmitted to the bi-metal element to spread the same and release the movable contact 39 and hollow tube 26..

From the foregoing it will be apparent that a plug type circuit breaker has been provided wherein the free tripping mechanism is received within a hollow button to reduce the size of the device, the free tripping mechanism being simple in construction and effective in operation to protect the breaker against damage as a result oi' improper manipulation.

Moreover, the invention provides an improved release mechanism wherein means is incorporated for adjusting the tension of the release spring 28 in order that the breaker may be set to operate under predetermined conditions. In addition to the foregoing, the free tripping mechanism embodies the hollow tube 3l! of insulating material which maintains the elements in proper y operative condition and enables the same to be actuated effectively as well as providing a design wherein the parts are fewer in number and more readily constructed and assembled than in devices heretofore provided.

While the invention has been described withI specific reference to the construction shown in the accompanying drawing, it is not to be limited, save as dened in the appended claims.

I claim:

1. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manual member to actuate the movable contact member and means within the movable contact member to render the man= ual member inoperative to actuate the movable contact member.

2. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in v,the casing, means to urge the movable member into open position, a manually operable member to actuate the mogble contact member, and means within the movable contact member to disengage the manual member from the movable contact member. 1

3. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable member to actuate the movable contact member, and means within the movable contact member and secured centrally of the stationary contact to disengage the manual member from the movable contact member.

4. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable member to actuate the movable contact member, and a,

tube secured centrally of the stationary contact and over which the movable contact member is slidable to disengage the manual member from the movable member.

5. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable'member toactuate the movable contact member, means on the manual member to engage the movable member, and a tube secured centrally of the stationary contact and over which the movable contact member is slidable to disengage the engaging means from the movable member.

6. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable member to actuate the movable contact member, and a tube secured centrally of the stationary contact and over which the movable contact member is Aslidable to disengage the manual member from the movable member, said tube being mounted with provision for a degree of movement with respect to the said stationary contact.

'7. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable member to actuate the movable contact member, downwardly extending arms on the manual member, detents on the arms to engagethe movable contact member, and a tube secured centrally of the stationary contact and over which the movable contact member is slidable to disengage the detents from the movable contact member.

8. A plug type circuit breaker comprising a casing having a i stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge the movable member into open position, a manually operable member to actuate the movable contact member, down wardly extending arms on the manual member, detents on the arms to engage the movable contact member, inwardly extending cam surfaces on the arms, and a tube secured centrally of the stationary contact and over which the movable contact member is slidable to engage the cam surfaces and disengage the detents from the mov@ able contact member.

9. A plug type circuit breaker comprising a casing having a stationary breaker contact mounted thereon, a movable contact member in the casing; means to urge the movable member into open position, a manually operable member to actuate the movable contact member, and downwardly extending arms within the manual member having detents thereon to engage the movable member.

lll. A plug type circuitbreaker comprising a casing having a. stationary breaker contact mounted thereon, a movable contact member in the casing, means to urge 'the movable member into open position, a manually operable member to' actuate the movable contact .memben downwardly extending arms in the manual member having detents thereon to engage the movable member, and means centrally of the movablel member to disengage the last named detents from the movable member.

1l. A plug type circuit breaker comprising a casing having a stationary breaker 4contact mounted thereon, a movable contact member in 'the casing, means to urge the movable member into open position. a manually operable member tov actuate the movable contact member. means within the manual member to engage the movable member, and means centrally of the movable member to disengage the last named engaging means from the movable member.

12. A plug type circuit breaker comprising a casing having a ntral stationary contact member at the bottom thereof, a tubular contact member slidably mounted in the casing -and adapted to be moved into contact with the stationary contact member and held in contacting position therewith, means to urge the tubular contact member into a disengaging position, a guide within the tubular contact member, a manually operable member. and means on the last named member to engage the tubular member.

13. A plug type circuit breaker comprising a casing having a central stationary contact member `at the .bottom thereof, a tubular contact member ,slidably mounted in lthe casing and adapted to be moved into contact with the stationary contact member and held in contacting y position therewith, means to urge the tubular contact member into a disenglmi position. a manually operable member, means on the last named member to engage the tubular member, a central member within the .tubular member and secured centrally oi the stationary contact .mem-

ber, and means cooperating with the last named central member to disengage the means to engage the tubular member.

14. A plug type; circuit breaker comprising a casing having a central stationary contact member at the bottom thereof, a tubular contact member slidably mounted in the casing and adapted to be moved into contact with the stationary contact member and held in contacting position therewith, means to urge the tubular contact member into adhengaging position, a manually operable member, means on the last named member to engage the tubular member, a central member within the tubular memberand secured centrally of the stationary contact member, and means on the manually operable member cooperating with the last named central member to disengage the means to engage the tubular member.

15. A plug type circuit breaker comprising a casing having a central stationary contact member 4at the bottom thereof, a tubular contact carrying member mounted in the casing with provision for axial motion and adapted to be moved into contact with the stationary contact member and held in contacting position therewith, means to urge the tubular member into a disengaging position, a guide within the tubular member, and a manually operable member to actuate the tubular member.

Lammer sommi'. 

